1. Field of the Invention
The present invention relates to organophilic clay complexes which are dispersible in non-aqueous fluids to form a gel therein. The invention also pertains to a process for preparing these novel organophilic clay gellants, and to non-aqueous fluid compositions including the same.
2. Description of the Prior Art
It is well known that organic compounds containing a cation will react with a clay under favorable conditions by ion exchange to form an organophilic clay. Furthermore, it is well known in the art that such organophilic clays can be used to thicken a variety of organic compositions. If the organic cation contains at least one alkyl group containing at least 10 carbon atoms, then such organoclays have the property of swelling in organic liquids. See for example, U.S. Pat. No. 2,966,506 and the book Clay Mineralogy, 2nd Ed., 1968, R. E. Grim (McGraw Hill Book Company).
It is also well known that such complexes may function to thicken polar or non-polar solvents, depending on the substituents on the organic salt. J. W. Jordan, in "Proceedings of the 10th National Conference on Clays and Clay Minerals" (1963), discusses a wide range of applications of organoclays from high polarity liquids to low polarity liquids.
The efficiency of organophilic clays in non-aqueous systems can be further improved by adding a low molecular weight polar organic material to the composition. Such polar organic materials have been called dispersants, dispersion aids, solvating agents, and the like. See for example U.S. Pat. Nos. 2,677,661; 2,704,276; 2,833,720; 2,879,229; and 3,294,683. The most efficient polar materials for use as such have been found to be low molecular weight alcohols and ketones, particularly methanol and acetone.
Furthermore, U.S. Pat. Nos. 3,977,894; 4,382,868; 4,464,274; and 4,664,820 describe the preparation of preactivated organophilic clay gellants that are used to thicken organic compositions wherein the activators are admixed with the organophilic clay.
More recently, organophilic clay gellants have been developed that are the reaction products of smectite-type clays having a cation exchange capacity with certain organic cations or combinations of organic cations and organic anions. These gellants have the advantage of being effectively dispersible in particular organic compositions without the need for a dispersion aid under normal shear conditions. Illustrative patents which describe such improved organophilic clay gellants are U.S. Pat. Nos. 4,105,578; 4,208,218; 4,287,086; 4,391,637, 4,410,364; 4,412,018; 4,434,075; 4,434,076; 4,450,095; and 4,517,112.
One way to enhance the gelling and dispersing efficiency of an organophilic clay is to replace some of the hydrophobic side groups attached to the organic cation with hydroxyalkyl groups. In these groups, the hydroxyl group is attached to any carbon atom on an aliphatic radical, except for the carbon atom adjacent to the positively charged atom, as disclosed in U.S. Pat. No. 4,434,076.
To further impart improved gelling properties, the groups attached to the organic salt may be replaced by a mono- or polyhydroxylated group. Modified organophilic clays containing these compounds swell and gel in organic liquids without the need for polar dispersion additives. For example, European Patent Application 0,133,071 describes modified organophilic clays resulting from the combination of a smectite clay, a quaternary ammonium salt having a long hydrocarbon chain, and a mono- or polyhydroxylated nitrogenous surfactant. The mono- and polyhydroxylated nitrogenous organic surfactants used in the disclosed formulations are ethoxylated amines and alkoxylated quaternary ammonium salts having long hydrocarbon chains, such as (tallow alkyl)- or di(tallow alkyl)-(methyl or benzyl) ammonium salts.
Further increases in the amount of alkoxylated groups, however, result in clay compositions that impart gelling properties to aqueous systems rather than to non-aqueous systems. For example, U.S. Pat. No. 4,677,158 describes a reaction product of a smectite clay and a quaternary ammonium compound that is used as a thickener for aqueous suspensions, particularly water based latex paints and caulks. The disclosed quaternary ammonium compound is said to consist of a nitrogen atom bonded to separate carbon chains where one chain can be a methyl group or an alkyl group containing 10 to 20 carbon atoms, and the second chain is an alkyl group containing from 10 to 22 carbon atoms or a polyoxyethylene chain. The third and fourth chains are polyoxyethylene chains such that the total number of ethylene oxide units is from 5 to 200 moles.
The disadvantages of most existing organoclay compositions for non-aqueous systems are that (a) relatively large amounts of the organoclay compositions are needed to impart the required viscosity; (b) polar activators are required in many cases to enhance their gelling properties; and (c) the organoclays are limited to either polar or non-polar systems depending upon their organic content.